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Abstract-A CMOS active pixel sensor that achieves wide intrascene dynamic range using dual sampling is reported. A 64 2 64 element prototype sensor with dual output architecture was fabricated using a 1.2-m n-well CMOS process with 20.4-m pitch photodiode-type active pixels. The sensor achieves an intrascene dynamic range of 109 dB without nonlinear companding.

One of the most important issues for researchers developing image processing algorithms is image quality. Methodical quality evaluation, by showing images to several human observers, is slow, expensive, and highly subjective. On the other hand, a visual quality matrix (VQM) is a fast, cheap, and objective tool for evaluating image quality. Although most VQMs are good in predicting the quality of an image degraded by a single degradation, they poorly perform for a combination of two degradations. An example for such degradation is the color crosstalk (CTK) effect, which introduces blur with desaturation. CTK is expected to become a bigger issue in image quality as the industry moves toward smaller sensors. In this paper, we will develop a VQM that will be able to better evaluate the quality of an image degraded by a combined blur/desaturation degradation and perform as well as other VQMs on single degradations such as blur, compression, and noise. We show why standard scalar techniques are insufficient to measure a combined blur/desaturation degradation and explain why a vectorial approach is better suited. We introduce quaternion image processing (QIP), which is a true vectorial approach and has many uses in the fields of physics and engineering. Our new VQM is a vectorial expansion of structure similarity using QIP, which gave it its name-Quaternion Structural SIMilarity (QSSIM). We built a new database of a combined blur/desaturation degradation and conducted a quality survey with human subjects. An extensive comparison between QSSIM and other VQMs on several image quality databases-including our new database-shows the superiority of this new approach in predicting visual quality of color images.

A CMOS active pixel sensor (APS) with in-pixel autoexposure and a wide dynamic-range linear output is described. The chip features a unique architecture enabling a customized number of additional bits per pixel per readout, with minimal effect on the sensor spatial or temporal resolution. By utilizing multiple readouts via real-time feedback, each pixel in the field of view can automatically set an independent exposure time, according to its illumination. A customized, large increase in the dynamic range can be achieved and a scene containing both bright and dark regions can be captured. A prototype of 64 64 pixels has been fabricated using 1-poly 3-metal CMOS 0.5 m n-well process available through MOSIS. Power dissipation is 3.7 mW at = 5 V. The special functions have been verified experimentally, and an increase of 2 bits over the inherent dynamic range captured is shown.

The work done to provide image sensors (CCDs and CMOS) with a wide dynamic range is reviewed. The different classes of solutions, which consist of logarithmic sensors, ''clipped'' sensors, multimode sensors, frequency-based sensors, and sensors with control over integration time are described. The pros and cons of each solution are discussed, and some new experimental results are shown. Active pixel sensors with a wide dynamic range are analyzed and possible future directions are pointed out. © 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)01610-4] Subject terms: image sensors; wide dynamic range; detector arrays; image quality; image reconstruction; very large scale integration; complementary metal oxide semiconductor image sensor; charge-coupled device; active pixel sensor.Paper 980463